TOI-157

TOI-157

TOI-157
Credit: L. D. Nielsen
Observation data
Epoch J2000      Equinox ICRS
Constellation Mensa
Right ascension 04h 54m 48.292s
Declination −76° 40′ 49.89″
Characteristics
Evolutionary stage subgiant
Spectral type G9IV
Astrometry
Proper motion (μ) RA: 11.849±0.013 mas/yr
Dec.: −18.732±0.013 mas/yr
Parallax (π)2.8128±0.0105 mas
Distance1,160 ± 4 ly
(356 ± 1 pc)
Details
Mass0.923 M☉
Radius1.0977 R☉
Luminosity1.106 L☉
Surface gravity (log g)4.3027 cgs
Temperature5629 K
Age12.82+0.73
−1.40 Gyr
Other designations
2MASS J04544830-7640498, TIC 140691463, Gaia DR3 4624979393181971328
Database references
SIMBADdata

TOI-157 (also known as TIC 140691463) is a G-type subgiant star located about 1160 light years (356 pc) from Earth. It has a mass of about 0.92 solar masses, a radius of about 1.1 solar radii and a temperature of about 5600 K. It is approximately 12.0 to 12.8 billion years old.

Planetary system

It has one discovered exoplanet orbiting it named TOI-157b. It is a gas giant classed as a hot Jupiter with a mass of 1.18 Jupiter masses and a radius of 1.286 Jupiter radii. It orbits very close to the star taking only 2 days to complete an orbit. This places the temperature of TOI-157b to be around 1588 Kelvin. Using TESS data discrepant transit parameters as well as empirical limb-darkening coefficients could be determined. Further analysis revealed that the radius ratio of planet to star is 7.8 ± 0.4 % higher than previously determined, caused by blending with the light from background stars, at a new value of 0.1229 ± 0.0005.

Age

It is a typical hot Jupiter. However, at an age of 12.82+0.73
−1.4 billion years the planet is currently the oldest discovered and only about 1 billion years younger than the age of the universe at about 13.8 billion years. Only PSR B1620-26 b with 11.2–12.7 Gyr remains as alternatively oldest exoplanet.